WO1999017985A1

WO1999017985A1 - Adjustable propeller unit which can be hydraulically reversed

Info

Publication number: WO1999017985A1
Application number: PCT/DE1998/002963
Authority: WO
Inventors: Gerd MÜHLBAUER
Original assignee: MüHLBAUER LUFTFAHRTTECHNIK GMBH
Priority date: 1997-10-02
Filing date: 1998-10-02
Publication date: 1999-04-15
Also published as: EP0941201A1; EP0941201B1; US6196801B1; ATE237497T1; DE59807959D1; DE19743739A1; DE19743739C2

Abstract

The invention relates to an adjustable propeller unit (20) for aircraft, land vehicles and watercraft which can be hydraulically reversed. Said adjustable propeller unit comprises a propeller with at least two blades, whose blade angle can be regulated by a control unit (regulator). A hydraulic connection exists between the rotating propeller and the stationary control unit for the blade drive. Said hydraulic connection has a spring loaded piston (4) which can be actuated by means of hydraulic fluid and adjustable mechanical stop motion devices for the start position (6), the brake position (8) and the travel or sailing position (5). The piston (4) is constructed as a spring loaded double piston comprised of an inner piston (19) and a ring piston (21) arranged around said inner piston. Both pistons can be locked with one another by means of a centrifugal force locking mechanism (22). In order to prevent uncontrolled reversing with revolutions above 1,500 RPM, the stop motion device (6) for the start position is constructed in order to limit the setting range of the locked double piston (4). The brake position can be obtained only when the inner piston is unlocked and the propeller revolutions are below 1,500 RPM when the propeller regulator is located in a high-pressure area.

Description

HYDRAULIC REVERSIBLE ADJUSTING PROPELLER UNIT

The invention relates to a hydraulically reversible adjustable propeller unit for air, land and water vehicles with a propeller with at least two blades, the blade angle of which can be regulated by means of a control unit (controller), a hydraulic between the rotating propeller and the fixed control unit for the blade angle control Connection exists with a spring-loaded piston which can be acted upon by a hydraulic fluid and adjustable mechanical stops for the starting position, braking position and / or travel / sailing position according to the preamble of claim 1.

To shorten the landing distances of aircraft or to improve the maneuverability of airships, amphibious aircraft or hovercrafts, propellers with a hydraulic device for reverse thrust (reversible propellers) are preferably used. There are various known devices and methods for this. These known devices and methods have certain advantages, for example the stepless preselection of the blade angle and the associated engine power in the so-called beta range (blade angle flatter than for the starting position) by means of only one power lever. However, these devices also have considerable disadvantages, for example a complex device for adjusting the blade angle, which is carried out via an adjustable hydraulic valve, that with the rotating propeller must be in constant communication. In many known engines, it is only possible with disproportionate effort to install such known systems. Faults in such a device pose a high safety risk in flight as well as in ground operation.

In a known hydraulically reversible variable-pitch propeller unit (DE-19600660), a stop is provided for the starting position, which is preloaded by disk springs, which can be overcome by means of a high-pressure hydraulic fluid to adjust the blade angle to the braking position (reverse) and apart from a mechanical stop for the braking position (reverse) is adjustable to create a negative boost.

Such a device eliminates the need for an ongoing, direct connection between the rotating propeller and the control unit (regulator) usually installed on the engine housing. If there is a loss of pressure, the blades automatically move from the negative blade angle back to a positive blade angle to ensure normal operation.

However, it has been shown that for certain uses of the variable pitch propeller unit, e.g. for seaplanes, the disc springs tend to corrode, which affects the operation of the variable pitch propeller unit.

It is therefore an object of the invention to develop a hydraulically reversible variable-pitch propeller unit of the type mentioned at the outset in such a way that operational reliability is increased, even when used in a damp or aggressive environment.

This object is achieved by the invention characterized in claim 1, ie in that the piston is designed as a spring-loaded double piston, consisting of an inner piston and an annular piston arranged around it, both of which can be locked together by means of a centrifugal lock, that the stop for the starting position is designed to limit the adjustment path of the locked double piston, to prevent unintentional reversing at speeds above about 1500 RPM and that the braking position can only be reached with the inner piston unlocked and propeller speeds below about 1500 RPM when the propeller controller is in the high pressure range.

In the variable-pitch propeller unit according to the invention, the plate springs of the known variable-pitch propeller unit can be dispensed with, since the propeller is adjusted in the reverse thrust by means of the inner piston arranged in the double piston, which is unlocked when a speed of less than approximately 1500 rpm is reached, so that with the Propeller controller in the high pressure braking position can be reached.

Advantageous refinements of the invention result from the subclaims.

According to a further advantageous embodiment of the invention, it is provided that the control unit (controller) is designed to create two different servo pressures which have a normal pressure for positive thrust for normal forward operation of approximately 12-22 bar and a high pressure for negative thrust for braking operation (Reverse) of approx. 32 - 48 bar.

A mechanical stop for the starting position is located in the hub of the propeller. The hydraulic control unit (controller) has two pressure relief valves, which in normal operation generates an adjustment pressure of approx. 12 - 22 bar for the double piston and in reversing operation an adjustment pressure of approx. 32 - 48 bar for the inner piston to the propeller blades in the so-called beta range to adjust to negative blade angle for braking position. The high-pressure hydraulic fluid is unregulated to prevent overspeed.

According to a further advantageous embodiment of the invention, it is provided that an electrically or mechanically controllable switching valve for switching the control unit from normal pressure to high pressure or from high pressure to normal pressure is provided.

According to a further advantageous embodiment of the invention, it is provided that a safety valve is provided in the control unit, which limits the pressure to normal pressure in normal operation in order to prevent the propeller from reversing unintentionally.

Finally, according to a further advantageous embodiment of the invention, a blade angle regulator can be provided in the control unit in the high pressure stage, which enables stepless blade angle adjustment in the beta range, depending on the servo pressure.

With such an arrangement, the hydraulic pressure assigned to the blade angle can be regulated in order to achieve a continuous blade angle setting in the beta range that corresponds to the engine power.

An embodiment of the invention is shown in the drawing and will be described in more detail below. Show it:

Fig.l is a sectional view of the propeller hub, wherein the variable propeller unit is in the position for large incline (sail position);

Figure 2 is a sectional view of the propeller hub with the variable propeller unit in the start position. 3 shows a sectional view of the propeller hub, the variable propeller unit being in the braking position; and

4a shows a schematic representation of the control unit in LP mode, and

4b is a schematic representation of the control unit in HD mode.

The adjustable propeller unit 20 shown in FIGS. 1 to 3 shows a possible embodiment of a reversible adjustable propeller with the essential parts of such a propeller, ie a hub 1, at least two blade bearings 2 for the propeller blades, flyweights 3, a servo piston 4 for blade adjustment, a mechanical stop 5 for travel or sailing position, a mechanical stop 6 for the start position, coil springs 7 and with a mechanical stop 8 for the braking position (reverse). The servo piston 4 is designed as a double piston, consisting of an inner piston 19 and an annular piston 21 arranged around it, both of which can be locked together by means of a centrifugal lock 22.

The hydraulic control unit shown in FIGS. 4a and 4b

30 shows a hydraulic propeller controller for constant speed with a pump 9, a normal pressure valve 10, a high pressure valve 11, a speed controller unit with adjusting lever 12, a regulator drive 24, a regulator spring 25, centrifugal weights 23, a switching valve for normal or high pressure 13, a servo pressure line for Propeller 14, return lines to the engine sump 15, a safety valve 16, a blade angle regulator 17 and with a supply line from the engine 18.

The mode of operation of the hydraulically reversible variable-pitch propeller unit 20 is described below.

The control unit (controller) 30 according to FIGS. 4a and 4b supplies the hydraulic adjusting device, ie the servo piston 4 of the propeller 20 with hydraulic fluid with two different pressures, as a result of which the propeller blades move over the blade bearings 2 and the centrifugal weights 3 attached to them in the direction of a small slope Adjust (start position) as long as the controller is in the underspeed state. The control unit (controller) 30 delivers the normal pressure in normal operation, which, depending on the engine power setting, ensures synchronous speed in the forward operation of the aircraft (vehicle). The hydraulic oil flows from the pump 9 through the high pressure valve 11 to the normal pressure valve 10 and from there through the speed regulator unit via the switching valve 13 to the servo pressure line 14. If the pitch of the blade is to be reduced, the switching valve 13 is actuated and the normal pressure line blocked. The hydraulic oil now flows from the pump 9 around the speed regulator unit directly to the switching valve 13 and further to the servo pressure line 14.

A system in which the oil pressure is used to reduce the slope is known per se. The pitch can move continuously between the adjustable mechanical stop 6 for the starting position and the adjustable mechanical stop 5 for the travel or sailing position.

If you want a flatter pitch than the starting position, e.g. To shorten the landing distance or for better maneuverability on the ground or in the water, the propeller blades must be able to be flattened to a negative blade angle. This is done according to the invention in that, as described above, the servo line for the first pressure relief valve 10 is closed for normal pressure and the servo line for the second pressure relief valve 11 is opened for high pressure via a switching valve 13. The switching valve 13 is activated either electrically via a switch or mechanically via an operating cable which can be attached to the engine power lever.

If the power lever is moved to idle and then pulled back towards the braking position (reverse), the high pressure line is activated. Since the propeller is in the underspeed state, the centrifugal lock 22 is unlocked and releases the inner piston 19, which can then move up to the mechanical stop 8 for the braking position (reverse). As a result, the propeller blades reach a negative blade angle and generate a corresponding braking thrust. The negative (braking) thrust depends on the engine power. This must be increased accordingly if the blades are on the mechanical stop 8 for the braking position (reverse). This is done in a known manner by means of a cam disk in order to enable the drive to be increased in order to increase the power even when the power lever is moved negatively. It is also advantageous that the high-pressure hydraulic fluid is not regulated by the speed controller. This avoids dangerous overspeeds that can occur with conventional brake position systems if a speed of more than 90% of the engine start speed is reached.

If you now want to move back from the braking position (reverse) to the starting position, the engine power lever must be moved forward in the direction of idling until the lock for the braking position has been overcome. The high-pressure servo oil becomes inactive and the blades are moved back to the starting position by means of the spring force when the normal pressure has been set, the centrifugal force lock 22 locking the inner piston 19 again with the annular piston 21 as soon as the speed has increased to about 1500 rpm becomes.

The braking position process is now complete.

This novel system according to the invention increases operational safety with the same level of security against unintentional braking position, since there is no need for a corrosive disk spring assembly. This simplification reduces the weight, the number of parts and thus the costs.

Claims

PATENT CLAIMS

1.Hydraulically reversible variable-pitch propeller unit for air, land and water vehicles with a propeller with at least two blades, the blade angle of which can be regulated by means of a control unit (controller), a hydraulic connection being established between the rotating propeller and the fixed control unit for controlling the blade angle , with a spring-loaded piston which can be acted upon by a hydraulic fluid in two different pressure ranges, and adjustable, mechanical stops for the starting position, the braking position and travel or sailing position, characterized in that the piston (4) as a spring-loaded double piston, consisting of an inner piston ( 19) and a ring piston (21) arranged around it, both of which can be locked together by means of a centrifugal lock (22), that the stop (6) is designed for the starting position to limit the adjustment path of the locked double piston (4) in order to be unbeabsic To prevent reversing at speeds above about 1500 rpm and that the braking position can only be reached with the inner piston unlocked and propeller speeds below 1500 rpm when the propeller regulator is in the high pressure range.

2. Hydraulically reversible variable-pitch propeller unit according to claim 1, characterized in that the control unit (controller) (30) is designed to create two different servo pressures which have a normal pressure for positive thrust for normal forward operation of approximately 12-22 bar and a high pressure for negative thrust for braking operation (reverse) of approx. 32-48 bar, the high-pressure hydraulic fluid being unregulated in order to prevent overspeeds in braking operation (beta range).

3. Hydraulically reversible adjustable propeller unit according to claim 1 or 2, characterized in that an electrically or mechanically controllable switching valve (13) for switching the control unit (30) from normal pressure to high pressure or from high pressure to normal pressure is provided.

4. Hydraulically reversible variable-pitch propeller unit according to one of claims 1 to 3, characterized in that in the control unit (30) a safety valve (16) is provided which limits the pressure to normal pressure in normal operation in order to prevent the propeller (20 ) to prevent.

5. Hydraulically reversible adjustable propeller unit according to one of claims 1 to 4, characterized in that in the control unit (30) in the high pressure stage a blade angle controller (17) is provided which enables a stepless blade angle adjustment in the beta range which is dependent on the servo pressure.